Alhazen pretended madness to escape from Egypt Ruler

Ibn al-Haytham (Alhazen).

Alhazen (965 – 1040) was an Iraqi Muslim scientist, polymath, mathematician, astronomer and philosopher. He made significant contributions to the principles of optics, as well as to astronomy and mathematics. He is known as the "Father of Modern Optics, Experimental physics and scientific methodology"

According to one version of his biography, overconfident about practical application of his mathematical knowledge, he assumed that he could regulate the floods of the Nile, a task requiring an early attempt at building a dam at the present site of the Aswan High Dam.
After being ordered by Al-Hakim bi-Amr Allah, the sixth ruler of the Fatimid caliphate, to carry out this operation, he quickly perceived the impossibility of what he was attempting to do. Soon he decided that the scheme was impractical and he feared the caliph's anger.
Fearing for his life, he feigned (pretended) madness. He was kept under house arrest from 1011 until al-Hakim's death in 1021. During this time, he wrote his most influential Book of Optics. After the death of Al-Hakim he was able to prove that he was not mad. After his house arrest ended, he wrote scores of other treatises onphysics, astronomy and mathematics.

The flooding of the Nile

The flooding of the Nile has been an important natural cycle in Egypt since ancient times. The first indications of the rise of the river may be seen as early as the beginning of June, and a steady increase goes on until the middle of July, when the increase of water becomes very great. The Nile continues to rise until the beginning of September, when the level that remains stationary for a period of about three weeks, sometimes a little less. In October it rises again, and reaches its highest level. From this period it begins to subside, and though it rises yet once more and reaches occasionally its former highest point, it sinks steadily until the month of June when it is again at its lowest level.

It would flood each year, bringing in silt-laden waters; when the waters receded the silt would stay behind, fertilizing the land, the silt would be helpful for growing crops. If a flood was too large it would wash over mud dykes protecting a village. A small flood or no flood at all would mean famine. A flood must be of just the right intensity for a good season. Without this flood cycle people would die from starvation.

In 1970, with the completion of the High Dam at Aswan, the annual flooding cycle in Egypt came to an end. Today, farmers must use fertilizers to keep their land productive, as the deposits of silt no longer occur each year.

Isis's tears of sorrow

Ancient Egyptians believed that the Nile flooded every year because of Isis's tears of sorrow for her dead husband, Osiris. Isis is an ancient Egyptian goddess and she was worshipped as the ideal mother and wife as well as the patroness of nature and magic. Osiris is an Egyptian god, usually identified as the god of the afterlife, the underworld and the dead.

Aswan High Dam in Nile – 3rd biggest in World

The Aswan High Dam is 3,830 metres (12,570 ft) long, 980 metres (3,220 ft) wide at the base, 40 metres (130 ft) wide at the crest and 111 metres (364 ft) tall. It contains 43,000,000 cubic metres (56,000,000 cu yd) of material. At maximum, 11,000 cubic metres per second (390,000 cu ft/s) of water can pass through the dam. There are further emergency spillways for an extra 5,000 cubic metres per second (180,000 cu ft/s). The reservoir, named Lake Nasser, is 550 kilometres (340 miles) long and 35 kilometres (22 miles) at its widest with a surface area of 5,250 square kilometres (2,030 sq miles). It holds 132 cubic kilometres of water.